Hello Glassparman,
it seems I have something like the same issue.
Also using groupjive 1.8b4 and CB1.2.1, and in the integration tab of groupjive settings, no way to select the forum type I want to use (may be Fireboard).

These releases will not work with Fireboard. There may be a way for you to hack it to get it to work, but this is not something the developers should be expected to take time to support.

I find it hard to believe Yahoo provides no way for their customers to use PHP5. Write them an email and ask how, and if they are so far beheing the times that they insist their customers are stuck with legacy technology you should vote with your wallet and change hosts.